


A Fair Deal

by Rush_Toward



Category: Undertale (Video Game)
Genre: Bullying, Character Study, Deal with a Devil, Dealfic, Demon Deals, Exploitation, Fake/Pretend Relationship, Forced Cohabitation, Hurt No Comfort, Implied/Referenced Character Death, Mental Coercion, Non-Sexual Intimacy, Non-Sexual Submission, Nonbinary Chara (Undertale), Other, Post-Undertale Neutral Route - Exiled Queen Ending, Power Dynamics, Power Imbalance, Psychological Drama, Psychological Torture, Soulless Frisk (Undertale), Tortured Sans (Undertale), Verbal Humiliation, Whump, secret keeping
Language: English
Status: In-Progress
Published: 2021-01-05
Updated: 2021-01-25
Packaged: 2021-03-15 09:09:17
Rating: Mature
Warnings: Creator Chose Not To Use Archive Warnings
Chapters: 4
Words: 13,443
Publisher: archiveofourown.org
Story URL: https://archiveofourown.org/works/28561092
Author URL: https://archiveofourown.org/users/Rush_Toward/pseuds/Rush_Toward
Summary: He thought it was over. Months had passed since the eighth human had taken what they wanted and crossed the Barrier, leaving the Underground more hopeless than ever. Sans’s life was just starting to regain some semblance of normalcy......but then the kid came back.
Relationships: Chara & Sans (Undertale), Chara/Sans (Undertale), Sans & Toriel (Undertale)
Comments: 10
Kudos: 25





	1. Malign

“Sans, I am home,” called an especially cheerful voice from the front entrance of Toriel’s house.

The smiling skeleton-monster mentally noted the current page number of the heavy book spread over his lap. “Hey Tori, welcome back,” he replied from his half-reclined position on the woolly round floor rug. Behind him, the fireplace shimmered and crackled with magic-made fire, casting a comforting glow throughout the room.

His smile faded slightly at the distinct sound of not just one, but two sets of footsteps approaching; one regal and measured, the other brisk and sharp. When he looked up to greet his friend and the guest accompanying her, it was like being plunged into an ice bath. The last thing he could have expected to see was the auburn-haired human hand-in-paw with Toriel, staring back at him expectantly. The fingers of their opposite hand were curled around the shoulder strap of a bulky green backpack.

“Hello again, Sans,” The Human greeted him without a moment’s hesitation. “I got your message.” Their casual tone and the sweet smile plastered across their face were betrayed by the cold glint of their eyes.

“Can you believe it?” gushed Toriel excitedly, releasing The Human’s hand. “Never would I have thought it possible for us to meet again, and yet here we stand!”

Sans momentarily felt as though he were dreaming.  Silently, he closed and set the book aside, getting to his feet.  Toriel’s smile wilted a bit at his lack of response,  her breathless elation threatening to fracture at what must have been a less-than pleased expression on his own face. Fortunately, a lifetime of practice allowed Sans to instantly relax his posture and adopt a friendly, unassuming smile.

“Well, fancy seeing you again, kid. What brings you back to the Underground?”

Contrary to his placid timbre, Sans inwardly fought to rein in his emotions at the sight of his brother’s killer.

The question cast a shadow over Toriel’s joyous visage, and she sobered up. “Yes, my child, you started to answer me earlier when I asked the same, but please explain it again. You were free of this terrible place, so why have you suddenly returned?”

“Well,” sighed The Human, mirroring the older woman’s seriousness. “I haven’t any family left on the Surface, and everyone I met down here was so kind to me. It was only after leaving that I realized how much I felt at home in the Underground. That’s why I decided to come back, this time for good.”

It had to be a lie. The Human wasn’t stupid. That message Sans had left on their phone’s voicemail months ago was a very clear warning to never return to the Underground. They wouldn’t disregard the subtle threat so easily.

It was a lie tailored specifically for Toriel, he realized, watching as glistening tears pooled in the motherly goat-monster's eyes in response to the lachrymose tale.

"Oh dear, I'm very sorry to hear how your life on the surface was not as happy as you deserve, my child, but I am so, so glad to have seen you once more."

Witnessing his best friend fall prey to The Human's emotional manipulation filled Sans with icy fury, but he bottled up the feeling before it could manifest in his body language.

The Human continued shamelessly spinning their narrative. "I thought about it for a while, and finally decided that this is where I belong. So, I took what I could carry with me and climbed Mount Ebott one final time.” They looked up at Toriel with wide, innocent eyes. “Don’t worry though; I have no intention of imposing on you. I’m prepared to be self-sufficient in every way. I just wanted to say hi before I headed out.”

“No no no, my child, goodness no,” Toriel immediately protested, and Sans did not miss the brief twitch of The Human’s lips at her dissent.

_ He’d rate their acting skills as a B- at best. _

Unfortunately he wasn’t their target audience; Toriel was, and she seemed sufficiently convinced by the performance.

Toriel clasped her massive furry hands to the front of her purple robe as she spoke, concern clouding her features. “I fear that your plan is too naïve. Things in the Underground are not the same now as they were when first you arrived. The people are more hostile towards humans than ever. If you were to step foot outside of these ruins, I have no doubt that something utterly terrible would befall you.”

Tilting their head, The Human gave her a wry look. “I know it’s dangerous, but I’ve already proven that I’m strong all on my own, haven’t I?”

“That is true, you certainly surprised me during our duel, and the very fact that you managed to traverse the entire Underground and escape with your soul intact shows how capable you really are. But even so, how do you propose to  _ live _ out there, for the rest of your days, amongst people who… perhaps rightfully so… blame you for their continued imprisonment?” The idea had Toriel visibly uneasy.

“The six human souls we collected vanished after you crossed the Barrier, along with the hope held by every monster in the Underground,” Sans interjected carefully. “Everyone hates you for crushing their dreams.”

Toriel cast him a wounded look, reproachful of his bluntness. “He is not wrong,” she admitted reluctantly. “And I think that for your own safety, it would be best that you stay here, with the two of us.”

As if having anticipated this, The Human gave a nod of agreement. “Well, you do know best,” they conceded, shrugging off the heavy backpack and leaning it up against the wall. “But only as a temporary arrangement. I already owe you so much, and I definitely don’t want to become a burden for you.”

“Never,” Toriel objected warmly. “Anyway! Are you thirsty at all, my dear? Hungry perhaps? Let me quickly whip something up for you.”

“Tea might be nice,” The Human suggested.

Toriel nodded happily and made her way into the kitchen. The Human’s eyes followed her momentarily before sliding over to Sans.

“So, why don’t you tell me what you’re really doing back here, huh?” Although his demeanor was amiable, Sans had never been more serious in his life.

“I told you; I got your message,” replied The Human with infuriating calmness.

“And I told you to stay out of the Underground.” He spoke softly, not wanting Toriel to pick up on the less-than-friendly nature of their conversation. “So for the last time; why are you here?”

“You’re not listening.”

The Human began to close the distance separating them, and the stout skeleton involuntarily tensed up as his fight-or-flight response kicked in.

“I said I got your message, Sans. In fact, I listened to it probably a dozen times every day. I heard what you said.”

The two of them were nearly nose-to-nose now; so close that Sans could practically count the long lashes lining their narrow eyes.

“You said to never come back here; that I wasn’t welcome.” They laughed lightly, warm breath ghosting over Sans’ face. “Isn’t that hilarious? You, trying to kick me out of my own home, I mean. It’s a funny joke.”

Disregarding the strange assertion, and knowing that he was playing into The Human’s hand, Sans still couldn’t help but growl, “It wasn’t a joke, pal.”

“Ah!” The Human nimbly leapt back a pace, smiling knowingly. “Don’t tell me you want to duke it out right here in Toriel’s house. I thought you were smarter than that, Sans.”

He realized with some alarm that he had indeed been a heartbeat away from initiating a fight with The Human, and he took a moment to calm down, breathing deeply to clear his head. He still had a lot of questions left to ask, yet also half a mind to simply vaporize the murderous brat and put an end to it all.

The sound of Toriel arranging dishware atop a serving tray in the kitchen convinced him that any course of action would have to wait until later. Sullenly he buried his fists in his hoodie pockets, keeping a watchful eye on The Human.

Toriel emerged a moment later carrying a decorative tray stacked with three piping-hot ceramic tea mugs and three plates each bearing a handsome slice of her homemade snail pie. “I thought we might all eat together!” she said happily, setting the tray down on the dining room table and beckoning the two of them to join her.

“Thanks, Tori.” Adopting his usual cheerful grin, Sans stepped past The Human with an easy gait. The prickling sensation in his spine from having his back turned to them was an unwelcome discovery, but he shrugged it off. Pulling out one of the heavy wooden chairs, he took a seat at the table and accepted the proffered mug and plate.

While The Human tore into their savory meal, Sans could only pick at his own generous slice, each bite sitting like ashes in his mouth. A familiar sense of powerlessness weighed down on him.

From today on he would be sharing a roof with the individual responsible for his brother’s murder. This was Toriel’s house, after all, and she had the final say. Masking his disquietude was proving more difficult than he liked, but for Toriel’s sake, and for the sake of bringing The Human’s true intentions to light, Sans hardened his resolve.

While Toriel watched The Human, Sans watched Toriel. For better or worse she seemed tickled pink at the fact that her would-be adoptive child had made a reappearance hearty and hale. He had never told her any of the terrible things The Human had done, knowing it would hurt her to learn that by protecting this human, she made herself indirectly responsible for dozens of monster deaths.

“My, I have not had so many people sit at my table in… quite a long while!” Toriel giggled musically, hands absentmindedly engulfing her otherwise untouched tea mug.

“I really missed your cooking,” the young human managed through a mouthful of chewy snail meat and flakey crust. “It’s the best.”

The praise had Toriel practically beaming. “Please, eat as much as you like, my child. I baked it just last night, and there is plenty more still in the kitchen.”

But The Human’s attention had already shifted over to the skeleton seated to their right. “You’ve barely touched yours, Sans. Wasting food is a crime, so I’ll eat it for you.”

Without providing him a chance to respond, they reached across the table and pilfered his meal, using their fork to nudge his plate’s contents onto their own.

“Oh my,” Toriel let out a small snort of laughter, biting her lip in amusement. “By the look of things, I will need to cook larger portions from now on if we do not want Sans to end up as nothing but bones!”

“Hey, no skin off my nose. The kid can help themselves if they want,” shrugged Sans breezily, balancing his fork atop two fingers. “I’m lucky enough to taste your cooking every day, and last I saw this one, they were eating dog salad and burgers covered in sequins. Plus, I figure climbing a mountain would work up anyone’s appetite.”

Below the table, Sans’ toes curled tightly in his worn slippers. He didn’t like it. Hardly twenty minutes into The Human’s arrival and they were blatantly trying to push him. The Human’s audacity had nothing to do with poor manners or the brazenness of youth. No, they were deliberately imposing their control over him, establishing dominance. The Human had already taken away so much from him, but evidently it wasn’t enough.

Maybe nothing was.

Leaning forward to rest both elbows on the table, Sans propped up his chin on one fist. "Speaking of, how was the trip here? Run into any trouble along the way?" The first thing that Sans had searched for were signs of dust on their clothing, but amazingly the kid was spotless. Of course, that didn’t mean diddly-squat if they had some ranged method of killing or simply cleaned themselves up before meeting Toriel.

This time they paused to actually swallow before speaking. "No, it was uneventful. Unlike before, no monsters got in my way."

He had to shut his eyes to conceal the hatred that would have shown in them. It seemed that fate never tired of toying with him. Why did Toriel have to care so much for this human? Not for the first time, Sans wished that he hadn’t kept his promise to her, and instead killed this creature the moment it stepped foot in Snowdin Forest. He knew, though, that doing so wouldn’t likely have made any difference. Not when dealing with a cheating time-traveler.

Regardless, Sans had no means of changing the past. What mattered now was to disinter The Human's motives. "Your bag over there looks pretty heavy," he remarked, indicating with a nod at the backpack still propped up on the wall in the far corner of the room. "I know I sure wouldn't want to hike up a mountain while lugging that thing along. Or at all." He winked for good measure.

Having completely cleared their plate, The Human set down their fork with a clink and wiped their mouth on the sleeve of their blue sweater. The angle of the light from the fireplace and the tilt of their head created a shadow over half their face. "Difficult situations become more manageable so long as you stay determined,” they informed him, as if it were the most obvious thing in the world.

With the meal now finished, Toriel made to gather up everyone's dishes, but The Human touched her hand to stop her. "I got it, Mom,” they chirped, stacking the dirty plates and mugs on the serving tray. “Washing these is the least I can do for you."

Their use of the title must have caught Toriel off-guard, because she blinked at The Human incredulously, a pleased smile spreading across her lips. “Why thank you, my child. You are so very good.”

“I’m happy to. After all, knowing how Sans is, you probably don’t get a lot of help around here,” they laughed flippantly to the monster woman as the two relocated to the kitchen.

Out of their line of sight, Sans narrowed his eyes resentfully, feeling an aching in his soul.

...The Human’s LV had increased since the first time he’d passed judgment on them.

**Notes for the Chapter:**

> Wrote this five years ago and never posted it, so here it is now. Is the Undertale fandom still alive?


	2. Simmer

The evening was spent in a leisurely fashion, whiling away the hours in front of the fireplace. Toriel regaled The Human with amusing anecdotes from her youth, and The Human occasionally interjected with well-timed questions or laughter.

Sans had reclaimed his book from earlier, although it was only for appearances now. He had no desire to join in on their conversation. While periodically turning a page to lend authenticity to the act, his thoughts and attention were focused primarily on The Human. 

All things considered, The Human’s current behavior made no sense at all. Previously they hadn’t wasted any time in making their way to the Capital in order to cross through the Barrier and exit the Underground. Yet a scant few months later they willingly returned, claiming they preferred it here to the Surface. 

Did The Human know that Toriel had once been wife to the King of the monsters? Sans couldn’t be sure. Most of the monsters living in the Underground wouldn’t recognize Toriel as their former Queen even if they met her in person. She had abdicated the throne more than two generations ago, leading a quiet life of solitude alone in the Ruins.

But Toriel knew, as did every other monster in the Underground, that King Asgore had met his end at The Human’s hands. She seemed resigned to the fact, and in truth, were it not for the fact that Sans had seen for himself just how deeply The Human’s cruelty ran, he too might have forgiven them for acting in what was certainly self-defense.

Forgiven them for killing Asgore, that was.  **Only** for killing Asgore.

Not for killing the other monsters, and  _ never _ for Papyrus.

It wasn’t in Sans’s nature to hate anything. Carrying a grudge was too much work, and in the months following his brother’s death, Sans had even begun to lose some of his resentment for a person who he assumed he’d never meet again. Acceptance was simply easier.

After all, humans were like a force of nature: unpredictable and unstoppable. What good did it do to hate magma for how it burned? Even though many monsters had tried their best to befriend the visiting human, their efforts had all been in vain. Sans sought comfort in the belief that nothing more could have been done.

After what had transpired today, though, he knew that he hated this human.

Forgiveness? The Human most likely wouldn’t even want it.

Listening in on the lighthearted exchanges between Toriel and The Human, it became apparent quite quickly that Toriel was deliberately ignoring the elephant in the room. Not a single mention was made of anything relating to the last time The Human had been in the Underground, nor of the tragedies which had occurred both during and after. It seemed that Toriel preferred not to address the issue beyond what had been discussed earlier in the foyer. She avoided using any variation of the word “trapped” when the topic of conversation shifted to The Human’s permanent change of address into the Underground.

For their part, The Human said very little about whatever they had done after returning to the Surface, and similarly made no mention at all of the injustices they had inflicted upon the innocent residents of the Underground.

Exiting through the Barrier was simply not possible without the combined power of both a human and monster soul, meaning the choice to re-enter came with irreversible consequences. Nearly, that is. Toriel’s unique Boss monster soul could be The Human’s ticket to freedom, if they ever changed their mind.

Still, assuming that The Human wasn’t simply insane, Sans doubted they had Toriel’s murder on the brain. When compared to a human’s superior strength, the power granted by a monster’s soul was minuscule, and likely would not provide any significant boost or utility besides simply granting passage through the Barrier a second time. But could he count on The Human to know this?

The skeleton monster flipped to the next page in the book, absentmindedly rubbing the aged paper between two fingers.

Toriel seemed truly happy. Happier than he had ever seen her, and she was never shy about reminding Sans how much brighter her life had become after befriending him.

Ever since moving in with Toriel, he had been extremely careful to hide from her the fact that the beloved brother who was the subject of so many happy stories he’d shared had died violently at the human-child’s hands. Twice a month Sans would exit the Ruins and travel to Snowdin village to collect things from his old house, swap out library books, and catch up on current events with the locals. Being no stranger to obfuscating the finer details of his personal life, Sans had taken to fabricating lies for Toriel of the “visits” he made to Papyrus while in the area.

He watched as she tenderly stroked The Human’s head, combing through their downy hair with her neatly-trimmed claws. The Human leaned into her touch, welcoming it, and Toriel’s eyes hooded contentedly.

It… ached a bit, to see another person so easily cheer her up better than he’d been able. The fact that the person was a dirty brother killer made the situation downright surreal.

Despite it being the driving factor behind the furious revolt that her own people had led against her after Toriel had re-assumed the throne in Asgore’s wake, she’d privately expressed her doubts to Sans regarding the accusations that her people still lobbied at The Human. Yet it was incontestable that The Human’s initial appearance overlapped with the sudden deaths of many monsters.

Sans had no such doubts. Most of the murders he’d witnessed with his own eyesockets.

Undyne, the Captain of the Royal Guard and hero to monsterkind.

Mettaton, the wildly popular idol robot with a soul.

King Asgore, who was like a father to countless generations of monsters.

Factor in dozens of random citizens from the more rural districts of the Underground, counted amongst which was Papyrus.

Given the evidence, Toriel had eventually conceded that it was possible for The Human to have played a role in some of the fatalities, particularly once she had viewed a recording of Mettaton’s final show. However, she stood firm in her insistence that they had merely acted out of self-preservation. Undyne and Asgore in particular would definitely have used lethal force against any human unfortunate enough to cross their path.

However, what Toriel couldn’t have known was that The Human was in possession of the godlike power to create and erase entire timelines. Exactly how the process worked was a mystery even to Sans, but what it ultimately meant was that The Human could freely pick and choose the outcome of any scenario they played a part in. Death itself wasn’t an obstacle for someone like that. Rather than resorting to homicide, The Human could have instead tried to escape from or reason with any monsters who engaged them.

So the ugly truth was that they just didn’t want to.

There were no clocks in Toriel’s house and no celestial bodies in the Underground to gauge the passage of time, but Sans’s circadian rhythm told him that night was setting in. A loud yawn from the young human resulted in a domino-effect as Toriel soon followed, covering her mouth modestly when the yawn morphed into a giggle. Sans didn’t resist a yawn of his own, and caught the older monster turning an affectionate smile in his direction. 

“Well, I think that is our cue to retire for the night,” sighed Toriel, rising to her feet. “Come, my child. Let us get you settled in. Will you be up much longer, Sans?”

“Hm? Nah,” he replied, pretending to have been engrossed in his reading. The Human was waiting patiently by Toriel’s side, and he met their eyes for just a moment before glancing away, trying to make the move look casual. “I think I’m gonna hit the hay, too.”

As they exited the common area, Toriel banished the magical flames in the fireplace and ushered The Human into the uninhabited nursery room. Sans slipped into his own bedroom, kicking his worn slippers off into one corner and heaving a weary sigh. Two walls separated his room from the nursery, but he could faintly hear Toriel’s soothing voice speaking to The Human from the other end of the hall, followed by the door gently closing. 

Sleeping was out of the question for him at the moment. Being in close proximity to a bonefied monster-killer filled him with nervous energy, and he wasn’t ready to lower his guard just yet. By their own account, The Human had taken his friendly warning as a challenge and personal insult.

He couldn’t pretend to be surprised, really.

Pushing aside a stack of borrowed books to clear some space, Sans hopped himself atop his desk, heels resting on the seat of a rugged wooden chair. Eyes closed, he tracked the familiar sound of Toriel’s graceful footsteps as she made her way to her own room. On some nights the former Queen would take a bit of time to write in her diary before going to sleep, but the excitement of today’s events must have tired her out, because without much further delay he heard the click of her lamp switch followed by the plaintive creaking of worn mattress springs shifting under her weight. With each of the three occupants in their respective rooms, total silence reigned over the dim house.

Nighttime tended to cause Sans’s thoughts to take a turn towards the depressing. He hunched forward, elbows resting on his knees, and laced his fingers in his lap.

Why had their LV increased? From killing Asgore? Impossible; the numbers didn’t add up. The EXP obtained from the King of all monsters was outstripped by the jump of their LV between then and now. Something else had happened. More importantly though, would Toriel be their next target?

Sans squeezed his hands together painfully tight. He couldn’t rule it out entirely.

His own safety was also a concern. The Human had made no bones about the fact that Sans was their raison d'être. What were they after specifically? His death? Awfully petty of them, if so, but if that  _ was _ all, then why bother with this transparent playacting? No, their roundabout approach suggested that it wasn’t a fight with him they were after; more likely they were simply interested in seeing him suffer. 

Truthfully, Sans didn’t want to fight. It wasn’t in his nature, and he had nothing to gain from it here. Even so, if The Human was looking for trouble, then he might just have to… disincentivize that particular course of action.

That would call for some creativity on his part. Reflecting on The Human’s behavior during their judgement in the Last Corridor, Sans concluded that they operated on a special kind of logic, far different from the norm. They were dangerously capricious. Behind that guise of playfulness, something truly menacing lay hidden, waiting to be freed. From the beginning, he’d felt an unsettling aura surrounding them, tinted with the suggestion of malice.

“Papyrus, what should I do?” he murmured in the dark. Pretending to speak with his brother every night was a little habit Sans had cultivated to help himself cope with the other skeleton-monster’s absence. Most often Sans would simply recount his day, sharing amusing exchanges he’d had with Toriel, or any interesting happenings (of which there weren’t many, as the Ruins were a very quiet and static environment). 

For each night of his first week living in this house, he had read Peekaboo with Fluffy Bunny aloud before bed, but had stopped after Toriel questioned him about it one morning. Apparently, he hadn’t been reading softly enough to avoid being overheard by his housemate in the adjoining bedroom. The conversation was ended with a white lie about how he liked reading himself a bedtime story to help fall asleep, and a polite refusal to her offer of reading to him herself.

Toriel knew he had a brother; he’d talked her ears off about Papyrus through the Ruins door back while he was still a sentry in Snowdin Forest. She knew they’d been close; more like best friends than just siblings. Sans felt terrible lying to her about his visits to Snowdin. Toriel was under the impression that the skeleton siblings spent time together, regularly enjoying each other's company. The truth was actually that Sans would idle at the spot where his brother had died, halfway between Snowdin and Waterfall, and remember.

“I know what  _ you _ would do,” he continued. “You’d believe in yourself, believe in The Human, and help them to become a better person. But I can’t do that. I’m not like you.” A wave of self-loathing washed over him, and he stubbornly fought against the negative sentiment, knowing Papyrus wouldn’t want him beating himself up over it.

“This is what happens when guys like me take it easy.”

That was his answer then, wasn’t it? Time for Sans to stop taking it easy. He would have to become more proactive from here out. A good first step would be to write up a sitrep on this new development.

He leaned over to pull open a slim drawer in the desk and lift out a thick binder. For a moment he simply held it in his lap and felt the faint hum of energy woven throughout its pages; powerful magic that belonged to someone who wasn’t around anymore.

The binder was made in a way where it synchronized across space and time with all the other infinite versions of itself. Changes made to the pages were reflected instantly, no matter where or when. This was a double-edged sword, because any damage incurred would be similarly reflected. For that reason, Sans had to be very careful to treat it delicately and to keep its existence a secret from others.

Another concern was the limited number of pages. Simply slipping a loose-leaf document between the album pages wouldn’t satisfy the magic’s requirements. Articles needed to physically become part of the book in order to persist through alterations to the timespace continuum. Sans tried to keep his logs brief to conserve space, and as such, there wasn't much in the way of discourse between him and his erstwhile selves.

Probably, Sans was going to need a better hiding place for this. Up until now, there hadn’t been any need; the possibility of Toriel snooping through his belongings was as good as zero. It was an altogether different matter now that The Human was back in their world, and living under the same roof.

Sans eyed the binder thoughtfully as he considered his options. How about a drawer with a false bottom? As far as tricks went, that was one of the oldest in the book, and there was the downside that he’d have to craft it himself without drawing any attention. Slipping the book under his mattress seemed positively sophomore; it’d be one of the first places that anyone would check when seeking to ferret out hidden contraband. Maybe it would be safest outside of the house, but that ran the risk of someone other than The Human happening across it without Sans even knowing. He supposed he could keep it in his dimensional box so that it was always on his person, but then that just passed the problem on to protecting access to his cell phone.

Anyway, it was definitely on the agenda. First things first.

Sans opened the binder and navigated through the pages that were clipped into three silver rings. The hybrid photo album / journal was comprised of transparent sheet protectors filled with printed documents and handwritten notes, as well as pocket pages holding photos both glossy and faded. The handwriting was recognizably his own, but he had no memory of writing them. This was because he hadn’t. All but the most ‘recent’ notations were the contributions of other Sanses from bygone timelines.

The very earliest entry in the journal, written by a Sans who had ceased to exist dozens of timelines prior, stated clearly that his decision to use the magical journal had come about as a response to the oppressive sense of déjà vu plaguing his daily life. Subsequent entries were marked with dates to chronologize the recorded events as well as indicate where each timeline diverged from the previous and the following. With this, Sans could identify trends and deviations in how events played out. Very likely there existed ‘older’ timelines which had never been documented, either from before he’d gotten the idea to start chronicling data, from instances where he was physically unable to do so, or if he simply didn’t see any need. The knowledge that some entity was playing with timelines didn’t necessarily make predicting the end of the world any easier. A sad reflection of Sans’s growing apathy, the level of detail found in his notes gradually declined up to the most ‘recent’ entries. 

When he reached a point where there was space available, he stopped and slipped the halfway-full paper out from its plastic sleeve. It took a moment to dig up a fountain pen buried under another stack of books nearby. Below the handwritten text  _ the human crossed the barrier _ , and  _ the six human souls disappeared _ , he tidily scrawled in the current date, followed by  _ the human came back. _ Before he'd even dotted the end of the sentence, it occurred to him then that he still did not know The Human’s name. When first introducing himself to them in the forest, he had deliberately neglected to ask for their name in return, because honestly he had not wanted to know. It was almost certain that The Human would simply die in the Underground and have their soul stolen. There was no point in asking the name of a dead person.

One more thing to add to the docket.

Coaxing the page back into its sleeve, his attention lingered on previous entries. Part of him wanted to reread through everything, but he knew it wasn’t a constructive use of his time. The Anomaly was two doors down, and it didn’t seem that Sans’s datakeeping would help the current situation. But maybe it would help the next Sans, so for now, he could at least do this much.

With that first order of business taken care of, there was something else he felt the need to do before calling it a night.

Sans used a shortcut to place himself in the hallway outside the nursery with such precision that even the aged wooden floorboards did not creak under the sudden added weight. Despite the door separating them, he kept his eyesockets dark, pupils extinguished. Holding perfectly still, he concentrated his magic into his sense of hearing, extending the level range to greater heights of sensitivity. He tuned out all unnecessary sounds: the intermittent creaks and groans of the ancient house, Toriel’s faint snoring, and the chirping of a multitude of crickets who populated the mountain’s inner caverns. With his full attention focused solely on The Human’s room, he listened for any suspicious noises or indications of potential danger.

The Human’s breathing pattern was slow and even; characteristic of sleep, at least for most monster types and hopefully for humans as well. Several minutes went by while Sans listened carefully, but he could detect no other sounds from within their room.

He almost wanted to scoff. Here he was getting bags under his eyes as he aged prematurely from stress, and the kid was snoozing peacefully without a care in the world. 

With a self-deprecating shrug, he took two steps towards the foyer and reentered the relative safety of his own bedroom. Bed didn’t seem so appealing when there was a murderer lurking nearby, but he could probably make sleep happen anyway. Not bothering to change out of his day clothes, Sans rolled onto the mattress and halfheartedly tugged the rumpled sheets over himself. Closing his eyes, he let out a sigh laden with weariness and willed his racing thoughts to settle. He’d deal with tomorrow when tomorrow came.

Just as the magic amplifying his hearing faded back to normal, he picked up a faint sound from down the hall, and his eyes flew open once more.

“Goodnight, Sans,” came the soft but unmistakable voice of The Human, ending in a short childish giggle.

A chill shot up his spine, and Sans barely suppressed a shudder.

_ Just great. _

*****

Sans woke to the sound of voices from the far end of the hall. It was commonplace for Toriel to start her day early, but she was never in the habit of talking to herself. Any hope Sans might have had that all of yesterday was simply a bad dream was quickly dispelled. With an invisible weight bearing down on his shoulders, he slid out of bed and found his slippers before heading out to the brightly lit hallway.

“No, child, this is not your mess to clean,” Toriel was saying to The Human in an authoritative and motherly tone. “I should not have let it get so dusty in here to begin with. Please, just relax and enjoy yourself. I’m sure even an energetic young thing like you still feels weary from climbing the mountain yesterday.”

She was holding a bucket of water and a pawful of clean rags as she strode into the nursery. The Human looked over to Sans instantly as he exited his bedroom, not arguing further.

“Hey Sans, Mom says I should go play while she takes care of things. Come for a walk with me so we can catch up on stuff.”

So, they were making their move already. From the first moment they showed up the kid was dropping hints left and right that they wanted to catch him alone. Sans had estimated that this exact suggestion would come about at some point during the next one to three days, but as he was quickly noticing, The Human was the impatient sort, never caring to stop and smell the cacti.

Sheesh, not even giving him time to eat breakfast first. For all he knew it could be his last meal.

“Sure, let’s go,” he answered in an amiable tone.

Anyway, resolving the situation while out of Toriel’s sight was in everyone’s best interests.

**Notes for the Chapter:**

> You think he can handle it?


	3. Compulsion

Trekking through the Ruins these days was much quicker thanks to the complete removal of the ancient traps. Disregarding public opinion, Toriel had committed to treating all fallen humans as friends, and the puzzles served no purpose for such a policy. She was no longer the Queen of the Underground, but she was still the caretaker of the Ruins, and this was her domain. Sans had assisted Toriel in disarming each of them a few months prior.

Sans found himself trailing behind The Human, who was striding confidently through the Ruins like they owned the place. And that presumption didn’t seem so far-fetched, as the usual Froggits, Whimsums, Vegetoids, and Looxes were nowhere to be seen. Nobody came to intercept The Human. Despite the absence of dust on their clothing when they’d first stepped past Toriel’s threshold, Sans had a hunch that the uneasy and desolate atmosphere pervading the magenta halls wasn’t for nothing.

After the blatantly threatening behavior The Human had exhibited towards him yesterday, Sans knew he was taking a serious risk in allowing himself to be led alone with them into the Ruins. The Human was demonstrably strong, and Sans’s combat skills were rusty from many months of disuse. When was the last time he’d been in a real fight? Or even a pretend one? It seemed like ages since he’d sparred with Papyrus; not since before Undyne had taken over his brother’s warrior training.

He tried not to think about that.

The Human’s surprise arrival also meant that Sans wasn’t permitted time to prepare for a scenario in which The Human intended to attack. Playing dirty would be imperative if he wanted even a snowball’s chance in Hell at lasting more than five minutes against this thing. He couldn’t afford to pull any punches. 

Contrary to The Human’s claim of wanting to “catch up”, they showed no interest in talking. Already past the midway point of the catacombs and not a single word had been exchanged between the two of them. Not that The Human was completely silent; Sans could clearly hear them humming a little tune to themselves as they practically skipped ahead.

Looks like initiating conversation was up to him.

“You know, I never actually caught your name.”

The humming stopped, along with their footsteps.

“It’s about time you got around to asking that,” they commented reproachfully, red eyes flicking in his direction from over their shoulder. “You monsters are so eager to introduce yourselves, yet none of you bothered to find out who I am. Although truthfully, I never minded being known as ‘The Human’. There are no others besides me, after all. But, I wonder who you think you’re asking, Sans.”

_Well that was a weird thing to say._ “Thought it was pretty obvious that I’m asking you.”

“Hmm,” they murmured almost under their breath, tapping a finger to their chin in contemplation. “What to do…? I could tell you my name, but would not want you using it around Mom.”

The skeleton-monster grinned icily. “Gotta say, you have some real nerve calling her that.”

Flashing him an unnaturally wide and toothy smile, they spun around and planted their hands firmly on their hips. “She likes it. She told me herself I could call her that, when I first fell down here. Why should I not?”

Sans ignored the question. It wasn’t important. “Seems a little inconvenient not to know your name if we’re going to be roomies. But hey, I’m not one to pry.” It was just a matter of fact, though his words might be interpreted as an attempt at reverse-psychology.

A tiny smile on their lips now, The Human indulged him anyway, their intense eyes boring into his own. They performed a strange sort of genuflection; a cross between a bow and a curtsy.

“My true name is Chara.”

There wasn’t a monster in the Underground who wasn’t familiar with the name ‘Chara’. It was the name of the adoptive child of King Asgore and Queen Toriel and adoptive sibling to the late Prince Asriel. The first and only human to hold a position of royalty over monsterkind, who had suffered an untimely death from accidental ingestion of poison.

"Y'know, that's interesting,” Sans drawled. “Back when I was still in school, we were taught that there was once another human in the Underground who went by the name of 'Chara', long, long ago. That Chara was a kid too, maybe even right around your age. Funny coincidence, huh?"

The Human's smile remained placid, their brow relaxed and unconcerned even as their eyelids slowly lowered tellingly.

Sans felt that the circumstances were unfolding into something more convoluted and unbelievable than he could ever have guessed. His gut instinct told him that this human—this **creature** —was far more dangerous than even he had given them credit for.

He dropped the pretense. “You’re no kid, that’s for sure. Are you even a human?”

“I was.” Chara sneered, beginning to pace, circling back around Sans without breaking eye contact. “I was, and I was, and if I’m something else now then that suits me just fine. I despise humans.”

“And that’s why you’re here, right?” He shrugged sarcastically. “You hate your own people so much that you figure, hey, better go dive down into a cursed mountain and apply for my monster green card!”

“Is that really so hard to believe? Have you any idea what it’s actually like on the Surface, Sans?” Their expression clouded momentarily, before they disregarded whatever memory must have come to mind and smiled at him once more. “The Underground is a nice place filled with nice people. You all think you want to leave, but you don’t.”

“Nice people, huh? You’re right. They are nice. So fill me in: if it’s humans who you hate so much, then how come you aren’t up there, taking your revenge on them instead? Why attack innocent monsters?”

Chara’s laughter was like the tinkling of a bell, resounding clearly throughout the rocky cavern. “Because it’s fun.”

Sans shook his head and sighed. “Shoulda figured as much. Someone like you? With that god-like power at your beck and call? Of course ‘fun’ would be all the justification you’d need to pull a stunt like this. Just because you ‘can’, you think you ‘have to’. To be honest, it’s really gross.”

“Well, that’s your viewpoint. I won’t judge you for it,” Chara intoned, mocking Sans with his own words from their final meeting months before. They looked infuriatingly self-satisfied.

Their pacing had placed Sans directly between them and the opposite end of the corridor the two of them had been heading towards. An anxious thrumming began in his soul as The Human made to close the distance separating them, expression still sphynx-like. Thus far, Sans hadn’t seen them brandishing anything more threatening than Toriel’s silverware during yesterday’s meal, and he quickly ascertained that both of The Human’s hands were empty of any weapons. Even so, his figurative hackles rose at their approach, and he braced for the possibility of a sudden attack. Sans already had a solid grasp of their fighting style after extensive observation. Bearing this in mind, he plotted three steps ahead for each of several maneuvers The Human might make, ready to take evasive action.

However, Chara simply pushed past him indifferently, and after another moment, Sans turned and resumed following.

This kid was really hard to read.

Soon they reached the end of the Ruins; the farthest possible point in all the Underground from the ancient, still-intact Barrier. Scant rays of sunlight filtered through cracks in the mountain top far above, providing high-contrast illumination over the area.

Chara moved briskly through the narrow passageway and into the dimly-lit cavern. Sans watched without comment as they tread carelessly on the beautiful flower bed. Disregarding—or perhaps relishing—how every step crushed several flowers underfoot, they walked to the very center of the garden. With a delighted sigh, they threw out their arms to the sides and spun in a circle with their eyes closed, twirling round and round.

“It feels so good,” they murmured, “To be on top of these flowers instead of under them.”

Sans was starting to reevaluate his stance on The Human’s ( _or whatever they were_ ) mental stability. He glowered as the delicate flowers that Toriel tended to so diligently every day were trampled and bruised. Then something at the rear of the cavern caught his eye. Along one rocky wall dangled the end of a thin rope, hanging between two ancient stone pillars. Tilting his head back, Sans followed the trailing rope upwards until it disappeared past a sea of stalactites.

So, they didn’t freefall into Mt. Ebott. The rope confirmed for Sans that this endeavor of theirs wasn’t exactly spur-of-the-moment. He briefly wondered if the rope was still there because they intended to climb back up, but no. They had to know that the all-encompassing Barrier would block escape. More likely they just didn’t see any reason to bother cutting it down.

Still spinning, Chara bent low to pluck one of the golden flowers from the patch and methodically detach each of its six petals, discarding them one at a time so they fluttered pitifully to the cave floor. By this point the flowerbed was in a state of disarray after being treated like a welcome mat, and Sans was getting pretty tired of just watching the kid mess around. 

“Hey. Why don’t you stop breaking things that don’t belong to you.”

At the sound of his voice, Chara slowed to a stop, rocking dizzily. “Shows what you know, Sans," they remarked, words tinged with annoyance. "It’s only because of me that these flowers are here at all. Well, and because of one other person, but he doesn’t matter anymore.”

Sans filed that bit of information away for later and rolled his shoulders to loosen them up. The Human certainly had him on edge. At least he’d gotten the creep talking again.

“I just want to point out that it’s awfully hypocritical for you, of _all_ people, to judge me for my actions,” Chara continued with a frown. “After all, you’re partially to blame for this ending. Someone ought to judge you for what you did, or more specifically, what you didn’t. I guess little old me will have to do.” And they tossed him a playful wink. “Sans, I find you guilty of being a lazy fool who chose to watch and do _nothing_ while innocent monsters died, including your own brother, all because of a meaningless promise born from ignorance. You knew exactly what was happening, and for that sin you alone bear responsibility.”

_Wow, they’d really gone there._ Seemed that the niceties were over. How they even knew about his promise to Toriel was anybody’s guess, but safe to assume it could be attributed to their special power. Closing his eyes, Sans shrugged indifferently. "You know what? I actually agree. Right from the moment we met, I should have done whatever I could to stop you. Guess I'm just too nice for my own good. But, better late than never."

When he opened his eyes again, the usual bright points of light had vanished, leaving only solid black pits of darkness. “NOW GET THE HELL OFF OF THOSE FLOWERS.”

Yanking his left hand out of his pocket, Sans instinctively focused his magic on The Human to initiate combat.

Yet... nothing happened. The Human’s soul did not appear, and they simply smiled innocently at his bewilderment.

"Hm, that's new," remarked Sans breezily, lowering his hand and feeling a trickle of cold sweat run down the side of his neck. "There something you wanna tell me, kid?"

Indulgently, Chara tugged the fuzzy collar of their sweater down far enough to expose a silver necklace lying against their chest. An ivory charm dangled from the chain, upon which Sans could just barely make out an engraving of a single human eye.

“I’m sure you know that humans have their own brand of magic," explained Chara unnecessarily, releasing the neck of their shirt. "It’s not as visually impressive as being able to manifest objects out of thin air or shooting complex bullet patterns, but still pretty useful.”

Apotropaic magic, Sans thought with a sinking feeling in his bones. He’d only ever read about it. The amulet was a ward which served to nullify monster magic, and while worn, it would not allow their soul to manifest outside the safety of their physical body. Similar magic had been utilized in the old war between humans and monsters. _So people living on the Surface still had a use for such things, huh?_

Inwardly he cursed. Considering that he hadn’t been afforded any time to prepare, the chances of defeating The Human in fair combat would normally be dubious at best, but this really iced the cake. He had to hand it to them; the kid sure thought this one through.

As if reading his thoughts, The Human spoke up. "Don't worry, Sans. I didn’t come here for the sake of fighting you again."

“What—” He cut himself off as the situation became clearer. This wasn’t the kid’s first rodeo. The Anomaly had been resetting timelines left and right. It didn’t take a genius to piece together that this human had played around with Sans this way before. And more than likely, the two of them had come to blows in at least one of those timelines. Sans cursed again. So, all his cards were laid on the table, then. The Human knew everything, while he was limited to making educated guesses at best.

“Welp.”

His frustration must have showed.

Their lips pulled back in a toothy grin as they shifted their feet to adopt a fighting stance. “If you’re dead-set on it, I do not mind playing.”

“Not really,” he answered with an unapologetic shrug. “Not at all, actually. I don’t like confrontation. You might say I’m a lover, not a fighter.”

Expression almost wry, they straightened again. “Why is it so difficult to motivate you into action? Why do you give up so easily, Sans?”

Oh no. They weren’t going to suddenly start with the armchair psychology, were they? He didn’t think he could stomach it. “I dunno, probably something to do with the fact that whether I work hard or not, there’s someone out there with the power to undo everything in the blink of an eye. It can get a little discouraging to be honest.” He knew his smile probably looked a little sad, but he couldn’t be bothered to correct it. “Y’know, I keep waiting for this timeline to end, like it has before, over and over again. Yet every day I wake up and I’m still here. Guess the Anomaly is finally satisfied with how things turned out, huh?”

The flash of vindication in The Human’s eyes was unsettling. “Would you like for me to Reset, Sans?” they asked very seriously.

God, and to think there was once a time when he would have given anything for the Resets to stop. “I’m positive that you didn’t bother coming all the way back here just to get my opinion on the matter.”

They hummed thoughtfully, clasping their hands behind their back and swaying from side to side. “After our little talk in the Last Corridor, I got to thinking. You said that anyone with my kind of power should exercise it responsibly, and you know, I think you were right. I feel bad about killing all those people and about reversing the progress that monsterkind had made towards breaking the barrier.”

“You. You felt sorry, after everything you’d done?” Could they possibly tell a more blatant lie? The expression on The Human’s face was so utterly devoid of remorse that Sans actually felt offended by the half-baked assurance. “Kid. Sarcasm isn’t funny.”

“Geez, Sans, if you keep doubting me like this, I might end up just changing my mind! The truth is, I’ve been considering Resetting the timeline to a point before you and I ever met. If I do, you’ll forget all about everything that happened in this timeline and resume living happily with your brother and all your friends in Snowdin. Your life would return to normal.”

The mention of his brother sent a lance of pain right through his soul. He forced himself to ignore the gut-wrenching sadness already welling up. Now wasn’t the time. “I thought you said you wanted to live down here.”

“Sans, Sans, perceptive as always,” The Human declared in a sing-song voice. “I will. Mom is the one who finds me after I fall. I’ll spend my days peacefully here in the Ruins with her.”

“I don’t get it. What difference is there whether you stay here in this timeline or in another? Things don’t change much in the Underground, y’know.”

“True, it might not make a difference to me, but it’d make a world of difference to you, Sans. Well, not to _you_ , specifically, but the new you. Old you. The next Sans.”

They were right, and there was his latest hint that they had something planned. Sure, it would make all the difference to the other Sans, but whether that difference was positive or negative depended entirely on The Human’s course of action in the fresh timeline. Sans had a strong feeling that he was being baited.

“So let’s just pretend I actually believe that cheesy sob-story you sold Tori about how you’re actually such a big fan of monsters and that you think of the Underground as your home. If you’re really willing to use that special ability of yours to make a new timeline and honor your word about not hurting anybody… Well buddy, I’d be a fool to try and stop you. But no offense, after everything I’ve seen, you don’t exactly have my vote of confidence that you’ll do the right thing the next time around.”

“Very astute. The fact is, I still need a little more convincing before I can agree to settle down for good, and I think you, Sans, are just the man for the job.”

Convincing them to play nicely was exactly what Sans had been trying to do since the very beginning, and he’d genuinely given it his best shot already. Frankly, he was sick of being jerked around by this human. Based on their choice of words there was obviously a condition, a trade-off that they sought in exchange for a Reset. There was still something here that they wanted.

Not good food, not nice friends, not bad jokes. Something else. And it related to him.

Such an obvious trap. He didn’t even need any further hints.

Sans wasn’t sure he wanted to hear what it was, but he had to ask. “What do you mean by that?”

Their eyes gleamed with something victorious. “Allow me to make a modest proposal. Something that I think it would be to our mutual benefit.”

The businesslike shift in their speech pattern threw him off a bit. He didn't like the way things were shaping up. “Alright. Lay it on me.”

“I believe in equivalent exchange. ‘You scratch my back, I’ll scratch yours’ and all that. Perhaps we can reach a compromise. I wasn’t lying earlier when I said this timeline was getting boring, but I don't like to Reset until after I’ve exhausted all sources of interest. There’s still something fun here, and that’s you.”

“Me, huh? And you say you didn’t come here to fight?” Sans eyed them skeptically. “Geez. I don’t know what else you’re expecting from me, unless you really like knock-knock jokes.”

“There is something I want you, specifically, to do for me. Something that no one else can.”

“And what’s that?”

Chara’s eyes danced with barely-restrained glee, and they leaned forward, lowering their voice. “I want you to beg for it.”

He almost laughed out loud. Of course they would need to go on one last power trip. But, he wasn’t someone who held pride so dear that he’d refuse to cooperate.

“Heh. Alrighty then. Please.”

The Human looked smug. “No.”

“No, huh?” He smiled humorlessly and shrugged. “Oh, my bad. For a second there I almost forgot what kind of person I was dealing with. Welp, if that’s how you want to play, then sorry, but I think I’m just gonna bounce."

This prompted a peal of laughter from them, the sound echoing off the rocky walls. “Oh, Sans. You always put such effort into maintaining your easy-going, good-guy image. Who would ever suspect that you have a stubborn streak? I know I didn’t at first.”

“So you like getting a rise out of people, huh? I gotta say, that’s a pretty messed-up hobby you got there.”

“I enjoy uncovering the truth,” they corrected. “And seeing the sides of people normally kept hidden.”

“Well congratulations I guess. Hope I was worth the effort.”

“Thus far, although I’m not done yet.”

“Yeah, well maybe I’m done. If you climbed this mountain just to gloat, then that’s your business, but frankly I’m getting tired of wasting my time.”

The laughter left their voice. “Now who’s the liar? You have nothing better to do. There is nothing left for you in this world. If I do not Reset, you will be trapped here for the rest of your life, bearing the weight of your sins.”

“Thanks for the reminder,” he remarked dryly. _Geez._ This person had committed unspeakable acts and they were seriously trying to pin it on him. He schooled his breathing, keeping it slow and even. This situation called for a cool head and zero chinks in his mental armor. “Tell me one thing. Have we had this conversation before?”

For one gratifying instant, surprise spilled across their face before it was quickly overwritten with amusement. “No, we haven’t. This is the first time.”

“Really.” He’d have to just take their word for it. “But despite that, you’ve known from the start what you’re going to do. Isn’t that right?”

They held out their hands magnanimously. “Not at all. Everything depends entirely on you, Sans. I’m offering you the opportunity to make things better. To have your brother back again. It’s up to you to accept my offer, or not.”

This entire exchange was wearing Sans down emotionally. He’d only been awake for half an hour and already he wanted to crawl back into bed.

“Explain it to me like I’m five. I wanna be sure I understand exactly what I’m agreeing to.”

From their rose-colored lips, they laid out their terms. “I will make you a fair deal, Sans. We needn’t fight each other any longer. Simply promise to do whatever I ask of you, and you'll have your Reset. Naturally, I will promise not to lay a hand on you or your brother in the new timeline.”

“Whatever you ask, huh?” he repeated. It was a ridiculous suggestion. There was no way he could agree to something as vague and broad as “whatever”.

The Human tilted their head knowingly at his obvious distrust. “If you are concerned that my requests will be unreasonable or land outside of your moral comfort zone, then allow me to put your mind at ease. I am fairly confident in my understanding of your limits, and I think I have a fairly solid grasp of what you would be willing to agree to.”

No doubt this understanding they boasted was all thanks to their cheap time traveling abilities.

“Since you say that you know so much about me, then you probably also know that I hate making promises.” And it was arguably a promise that had led to this awful situation in the first place.

“I also know that you are willing to make exceptions to that.”

“Hmmm.” He pretended to mull it over. “And what if I just say no? What's your plan B, kid?”

“You are not lacking in imagination, Sans. Why don't you take a guess? I think you already know the answer to that question.”

He nodded. Oh, he knew. He knew that The Human would casually slay Toriel, absorb her Boss monster soul, and cross the Barrier back to the surface world, leaving the Underground in absolute despair like abandoned garbage.

“I think it is a very fair deal. What else have you to lose?”

Good question. What did he have to lose? What did anything that happened from this point on even matter? For a while now, Sans had been lost in a way like never before. Life had come to a strange stand-still after Papyrus’s death. Every day in the Ruins was just like the last, as if none of it was even real. Before, there had always been a clear goal for Sans to work towards, whether it was his studies and research or just ensuring his brother's happiness. Now, Sans had even quit doing his comedy shows at the MTT Resort, since lowered public morale resulted in a plummet of attendance rates.

This person had taken everything away from him. But they could also give it back. They were promising as much, for whatever their word was worth. If there was a chance that the horrible fate which had befallen the entire Underground could be undone, and that some version of himself could be at least somewhat happy… If he were the only person in the world whose actions could change this horrible fate...

Then he was practically obligated to agree. Wasn’t he?

The Human was waiting for his answer. “Come now, Sans. Say yes, and I’ll erase this worthless timeline where your brother no longer exists. I’ll Reset, and you’ll have each other back again, safe and sound.”

Life in the Underground was pretty much already at—heh—rock-bottom. So he'd satisfy this creature, give them whatever it was they were hoping for, and… well, it would mean saying goodbye to Toriel, but not forever. They would always meet again.

“Fine. We got a deal.”

They inhaled sharply, clearly satisfied. “Good. Shall we shake on it?”

Against his better judgement, he took their small, pale hand and shook it once.

“Alright, kid, enough with beating around the bush. Go on and… tell me what you want, already,” said Sans heaving a weary sigh, avoiding looking at The Human as he voiced his submission. He didn’t even need to see them to feel Chara’s smile widen in response, as if it were a physical invasion of his personal space.

“Take off your clothes.”

**Notes for the Chapter:**

> for every 1 kudos sans takes off 1 sock can we get 5 kudos please


	4. Profane

“Take off your clothes.”

Well, that was one heck of a bomb drop.

Sans stared in stark disbelief at the young human. “You, uh, wanna run that by me one more time? Pretty sure I didn’t hear you right.”

“I said, I’m interested to learn what a skeleton monster looks like in the nude,” they elaborated unnecessarily, a hint of a leer creeping across their round face.

Despite everything, Sans broke into laughter. He’d already been bracing himself in anticipation of some outrageous demand from the deranged creature, and yet they still managed to catch him off-guard. It was just another reminder that Sans should stop underestimating the human.

“Seriously?” He cast a scrutinizing eye on them, cocking his head to one side.

“Indeed,” they nodded, auburn brows raised earnestly. “That is what I want. Get undressed, Sans, so I can see how you look without clothing.”

They were impressively brazen in their demands. He almost appreciated the frank honesty, though not nearly enough ( _ not in a million years, not in a thousand timelines _ ) to sway his opinion of the human as anything other than complete scum. Sans’s ranking of virtues had undergone some restructuring as of late, and good intentions stood head over shoulders above simple honesty.

“Wow. I don’t know whether I should be grossed out or flattered. After all this time, you came all the way back here just to get an eyeful of my old bones?” He winked at them playfully.

“If you prefer to think of it in such terms, then I don’t mind. Don’t worry, Sans,” they assured him with a sly smile. “I won’t touch you.”

He probably couldn’t stall any longer than he already had. The ball was firmly in his court, and he had a decision to make.

“Let me just make sure we’re both on the same page. You’re saying that in exchange for me doing this, you’ll Reset the timeline and promise not to hurt anyone in the Underground?”

“Exactly right. It’s a trade. You get what you want, and I get what I want. Quid pro quo. I think it’s a pretty good deal for you, honestly. A fair deal. Everyone wins.”

“Sure. When you put it like that, everybody wins.”

_ Just a little humiliation in exchange for another chance at a happier future. No biggie. _

“There’s one little problem though. I’m not going to remember any of this after you Reset, and you know that. So tell me, what’s left to hold you to your promise after this?”

It was a hopeless question, of course. This was all just a game to the human; a fun little way for them to kill some time. If they so desired, they could kill something else instead. It was well within their power to dust not just him and Toriel, but every last monster living in the Underground. They had the strength, they lacked the compassion, and with the ability to rewind time they had an impossible edge in terms of planning ahead and circumventing even their own death.

“Sans, my word is my bond,” they insisted, laying a hand over their flat chest. “Think what you will of me, but I always keep the promises I make. If anything, you’re the one whose integrity should be called into question. After all, you promised Toriel that you’d protect any human you met, but just a moment ago you tried to attack me.” They laughed softly through their nose. “Fortunately for both of us, this exchange requires that you uphold your end of the bargain before I must uphold mine, so it’s not a problem.”

_ If there was a God, then they must have hated monsters, to let them lead such a miserable existence for so long, subject to the cruel whims of these humans. _

“Welp, you’ve managed to convince me. Let’s get this show on the road.”

There was nothing uncertain about how much he really, really didn’t want to do this thing. Even more certain, though, was the horrible reality that he couldn’t say no.

Sans started shrugging out of his jacket, resolving to treat the situation like a visit to the doctor. Heh… he’d always avoided doctor’s offices, though.

“Ah, wait.” Their voice was cheerful, yet something about it compelled him to freeze, long sleeves bunched up around his wrists.

“I can’t see very well when you’re standing in the darkness like that,” they pouted. “You can continue after you’ve moved into the light.” Stepping back a few feet, they motioned that he should take their place on the flower patch.

The rebellious side of Sans’s personality was tempted to refuse, but he immediately dismissed the impulse. It wasn’t worth it. Slowly, he made his way over.

For a moment he idled at the edge of the garden. It was already messed up from the human’s frivolous trampling earlier, and he was reluctant to make it any worse. Stupid of him to care, when these flowers would soon cease to exist along with everything else here. He stepped into the middle, treading as lightly as possible to minimize the harm done, but it was inevitable that some additional damage would still result from it.

To the flowers,  _ as well as to... _

The human nodded approvingly. “Much better. With that spotlight overhead, it practically seems like you’re up on stage!”

The last thing he wanted to be reminded of was the fact that he had an audience for this, let alone of who specifically comprised that audience. He kept his gaze anywhere but on the human, trying to shut out his thoughts and pretend he was alone.

Sans’s arms moved almost robotically, shrugging off the faded blue hoodie and letting it crumple to the ground, landing with a dull  _ fwup _ . There was a beat of hesitation as his fingers grasped the hem of his t-shirt, but then it too was yanked over his head and discarded onto the golden flowers. The human hummed thoughtfully as he exposed himself.

The off-white of his bones stood out in stark contrast to the black of his shorts and the surrounding shadows. Scattered beams of sunlight passed through the spaces between his ribs to cast stripes of gold across the cavern floor. He prayed that no other monsters would pass by this way. Surely they wouldn’t; everyone in the Ruins understood that this place belonged to Toriel, and they respected that fact. Even knowing this did not put Sans’ mind at ease, and he kept his ears perked up to catch the potential sound of any surprise visitors coming from the end of the dark hall.

The worst outcome imaginable was the possibility that Toriel of all people would come here and see what was happening. If she did, Sans was prepared to give one of any number of lies to explain away the situation, depending on the older monster’s reaction. He hoped it wouldn’t come to that, both for the sake of his dignity and his peace of mind. He’d told her far too many lies already.

Sans’s hands idled at the waistband of his shorts. The dimness of his surroundings made him feel a bit drowsy, but the nervous pounding of his soul kept him from relaxing. He was simultaneously hyper aware of his surroundings yet also felt oddly detached. This particular cavern always smelled damp and earthy compared to the rest of the Ruins since it was connected to the opening at the top of the mountain. He could hear a faint rushing sound from above, likely caused by a breezy wind, and could almost imagine the rustling of leaves from surface trees; things that monsters didn’t have the privilege of experiencing.

“Hey.” The human’s impatient voice broke him out of his reverie. Their characteristic smile was turned upside-down. “Don’t keep me waiting, Sans.”

Irritated, he hooked his thumbs under the elastic and shimmied out of his pants, leaving him clad only in his slippers and an old pair of bone-print boxer shorts.

“Keep going,” goaded the human immediately, not allowing him any time for second thoughts.

So much for leaving anything to the imagination. Taking a deep breath to ground himself, Sans yanked his boxers down to his ankles and kicked them off to join the rest of his clothing. He folded his arms across his chest assertively and stood up to his full height.

Under normal circumstances, he didn't give a hoot what he looked like. What counted most was what a person had on the inside; the content of one’s character. Still, the human’s piercing stare had him feeling acutely self-conscious.

“Is this about what you expected?” he quipped, completely disinterested in their answer.

Chara took a step to the side, followed by another, slowly, like a shark circling its prey. Sans resisted the urge to turn around with them, instead focusing on the vibrant garden at his feet and clenching his fists tight enough for the bones to creak. The flowers almost seemed to stare back up at him.

The human halted their pacing. “You’re so short,” they commented, almost accusingly. “How old even are you?”

“Old enough.”

“Old enough for what?”

“To party,” Sans answered dryly.

They let out a bark of surprised laughter. “Well anyway, it’s appealing in its own way. Your shortness, I mean.”

“Lucky me,” he muttered.

Their smile seemed wooden like a mask, and their eyes were cold. “A word of advice, Sans: you will want to stay on my good side. Otherwise, when I do Reset, I might decide not to kill Papyrus again. I will do something  _ worse _ .”

“Cut that out,” Sans sighed, his patience frayed. “You can’t expect me to believe that you’ll make good on your word when you turn around and say psycho stuff like that.”

The aura of malice surrounding them vanished in an instant, and they smiled at him beatifically, cheeks flushed an attractive rosy hue. “Relax, Comedian. It was just a hypothetical. You don’t actually have to walk on eggshells around me. Just uphold your end of our bargain, and so too will I. Trust me.”

“A fickle little thing like you? Someone with Godlike power and zero accountability?” He mirrored their smile. “Sure, I trust you. ‘Course, for all I know, you’ve already fed that exact same spiel to a different Sans and this is just a rerun episode.”

They made a small sound of laughter. “Pfft. Don’t flatter yourself. I am easily bored, and this is the first time I’ve propositioned you like this.”

Sans nearly choked in horror when he felt a soft touch on his upper arm. One of the human’s hands was on him, and their eyes were trained on the bone under their fingers. They didn’t linger for long, trailing their hand over his shoulder and around to his back, fingering his ribs and spine curiously. The gesture itself was nothing too intimate or invasive, and yet the feather-light exploratory contact felt alarmingly possessive. Sans resisted the urge to flinch away, directing his glare at the cavern wall where they wouldn’t notice.

“Thought you said you wouldn’t touch me.”

“Then I guess we’re both bad at keeping promises,” Chara whispered. But to his immense relief they backed off.

He suppressed a shudder at the lingering sensation of their hands on his body. “Anyway, are we done here? Have you had your fill of being a creepy freak yet?” It wasn’t a smart move, using anger to drown out his anxiety at being so vulnerable and on display.

But they only laughed at the insult, obviously not offended at all. “Yes, Sans. That’s enough for now. Consider our session over.”

Well, that sure sounded ominous. His chest pulled tight with apprehension. “In that case, I think it’s high time for you to keep your promise and do the Reset.”

Chara reached up high over their head, stretching blissfully. “Hmm, no, not yet.”

Sans could only stare, feeling an unpleasant mix of emotions welling up at this completely unsurprising betrayal. “We had a deal.”

The human glanced back at him, cruel amusement stamped all over their features. “Don’t jump to conclusions. The deal is still on. I just want to hang around a little longer before ending everything, that’s all.”

At the first sign of their waning interest in him, Sans snatched up his scattered clothing and redressed himself. And yet, somehow every time the human’s eyes met his own, he felt naked all over again. He shoved his shaking hands into his hoodie pockets, elbows drawn close to his sides. 

Sans was no hero, and he didn’t want to be either.

He knew he’d been dealt a shit hand for going up against the Anomaly, while life had favored them with a royal flush. No point in complaining. More importantly, every other monster unlucky enough to cross paths with this person or foolish enough to stand in their way was nothing but dust and a memory, yet for some reason Sans and Toriel were the exception. It was important that he choose his words very carefully here. Any hostility on his part—actual or perceived—could trigger another wave of death and suffering for the people trapped in the Underground. 

Like playing a game of Jenga, one wrong move and everything would come crashing down on him.

It was just so heavy a burden.

As if sensing a hole in his defenses, the kid drew closer, smirking at the way Sans shrank back in revulsion.

“I know you won’t tell Toriel about this,” they cooed. “You want to protect her from the harshness of reality; keep her in blissful ignorance. I agree, by the way. Toriel deserves to be happy. We shouldn’t take that away from her.”

Normally Sans was good at reading people, but he found it difficult to accept that anyone, human or otherwise, could be so deliberately cruel for no apparent reason. Then again, maybe it was just a human trait. He gritted his teeth. “If that’s how you really feel, then maybe you should quit doing stuff that you wouldn’t want her to know about.”

The human hummed as if pretending to consider this. “You’re not wrong, but as long as all of this stays our little secret, then there’s no reason for me to hold back.”

The breathy exhalation that hissed through Sans’ teeth was laden with defeat, and the sound made Chara’s lips curl up at the corners.

“Anyway. You can go back home if you want. I’m going to hang out for a while longer,” they announced dismissively. “Just remember what I said about using my name.”

Sans didn’t have to be told twice. He had never used a shortcut so fast; warping out of the ruins and all the way back into his bedroom in Toriel’s house. The sight of his bed made his knees go weak and give out beneath him, and he landed with a clatter on the wooden floor, hands clutching at the messy blankets.

It was only here, in the relative security of his own bedroom, that he finally allowed himself to acknowledge his fear. Each breath came faster and harder than the last, until his chest was heaving and his shoulders quaking uncontrollably. In the midst of his turmoil, one thought stood out clearly:

_ Sans had made a deal with the Devil. _

And it wasn’t over yet. He’d been a complete idiot to not see this from a mile away. The human wasn’t going to be satisfied so easily. They were the kind of person who  _ never _ had enough.

There was no foreseeable limit to his end of the deal. It would only be over when Chara said it was over, assuming they ever did.

“Sans? Are you home…?” Toriel’s head suddenly peeked curiously around the doorway and into his room. He barely managed to scrub away all the sweat with his sleeve before turning around to greet her.

“Heeey, Tori,” he waved, inwardly cringing as his voice cracked. “Yeah, I just got back. Sup?”

She frowned at him a little, her intelligent eyes lingering on his face in a way that made it readily apparent to Sans that she noticed something off about his behavior. Even his best performance couldn’t fool Toriel 100% of the time. Thankfully she didn’t pursue whatever suspicions she might have had. “I did not even hear you walk inside. Are you alone? I would have expected the two of you to return together…”

“Oh!” he said, a little too loudly, and cleared his throat. “Yeah, the kid wanted to hang out for a bit on their own, so I just came back by myself. You don’t have to worry about them; we both know the Ruins aren’t all that dangerous anymore.”

“Yes, I suppose that is true. Well, I am not quite done with my cleaning yet, but I have made significant progress, so it should not be much longer now!” She clapped a furry paw over one bicep and gave a huge wink to him. Despite everything that had happened that day, Sans managed a genuine, if weak smile in return.

_ He couldn’t let her know. _

  
  


**Notes for the Chapter:**

> Choo-choo all aboard the pain train


End file.
